LazyGrid in Android Kotlin - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ ui_behavior

intermediate

What is the visible item count in this LazyVerticalGrid?

Consider a LazyVerticalGrid with 3 columns and 10 items. Each item is a fixed size box. How many items will be visible on screen if the grid height fits exactly 4 rows?

Android Kotlin

LazyVerticalGrid(columns = GridCells.Fixed(3)) {
  items(10) { index ->
    Box(Modifier.size(100.dp)) {
      Text("Item $index")
    }
  }
}

A 12 items

B 10 items

C 9 items

D 15 items

💡 Hint

Think about how many items fit in each row and how many rows fit in the visible height.

With 3 columns and 4 rows visible, up to 3 * 4 = 12 items can be shown. Since there are only 10 items, 10 items will be visible.

❓ lifecycle

intermediate

When does LazyVerticalGrid compose items?

In Jetpack Compose, when does LazyVerticalGrid compose its child items?

A Only the first item initially, then others on demand

B All items at once when the grid is first displayed

C Only the items currently visible on screen and a few extra for smooth scrolling

D Items are composed randomly regardless of visibility

💡 Hint

Lazy means it does not create all items immediately.

LazyVerticalGrid composes only visible items plus some buffer items to optimize performance and memory.

📝 Syntax

advanced

Which code snippet correctly creates a LazyHorizontalGrid with 2 rows?

Select the Kotlin code that correctly creates a LazyHorizontalGrid with exactly 2 rows.

A

LazyHorizontalGrid(rows = GridCells.Fixed(2)) {
  items(5) { Text("Item $it") }
}

B

LazyHorizontalGrid(columns = GridCells.Fixed(2)) {
  items(5) { Text("Item $it") }
}

C

LazyHorizontalGrid(rows = 2) {
  items(5) { Text("Item $it") }
}

D

LazyHorizontalGrid(GridCells.Fixed(2)) {
  items(5) { Text("Item $it") }
}

💡 Hint

Check the parameter name for rows in LazyHorizontalGrid.

LazyHorizontalGrid requires the 'rows' parameter with GridCells.Fixed or GridCells.Adaptive. Option A uses correct syntax.

❓ navigation

advanced

How to preserve scroll position in LazyVerticalGrid after navigation?

You navigate away from a screen with a LazyVerticalGrid and then return. How do you preserve the scroll position of the grid?

A Use rememberLazyGridState() and pass it to LazyVerticalGrid's state parameter

B Use rememberScrollState() and pass it to LazyVerticalGrid's state parameter

C Save the scroll position manually and scroll to it on return

D LazyVerticalGrid automatically preserves scroll position without extra code

💡 Hint

There is a special state class for LazyGrid scroll state.

rememberLazyGridState() creates a state object that tracks scroll position and can be reused to restore it.

🔧 Debug

expert

Why does this LazyVerticalGrid crash with IllegalArgumentException?

Given this code, why does the app crash with IllegalArgumentException: 'GridCells.Fixed must be greater than 0'?

Android Kotlin

LazyVerticalGrid(columns = GridCells.Fixed(0)) {
  items(5) { Text("Item $it") }
}

A LazyVerticalGrid requires GridCells.Adaptive, not Fixed

B Text composable inside items must have a Modifier

C The items count must be greater than the number of columns

D GridCells.Fixed cannot be zero or negative; it must be at least 1

💡 Hint

Check the parameter passed to GridCells.Fixed carefully.

GridCells.Fixed(0) is invalid because the number of columns must be positive. This causes the IllegalArgumentException.